MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : Advanced IC Engine

Unit : I – Spark Ignition Engines

Topic of Lecture: Introduction

Introduction :

A heat engine is a device which transforms the chemical energy of a fuel into thermal energy and uses this

energy to produce mechanical work.

Prerequisite knowledge for Complete understanding and learning of Topic Gear terminology

1. Classification of Engine

2. Working Principle of SI Engine

Detailed content of the Lecture:

A heat engine is a device which transforms the chemical energy of a fuel into thermal energy and

uses this energy to produce mechanical work. It is classified into two types-

(a) External combustion engine

(b) Internal combustion engine

External combustion engine:

In this engine, the products of combustion of air and fuel transfer heat to a second fluid which is the working

fluid of the cycle.

Examples:

*In the steam engine or a steam turbine plant, the heat of combustion is employed to generate steam which is

used in a piston engine (reciprocating type engine) or a turbine (rotary type engine) for useful work.

*In a closed cycle gas turbine, the heat of combustion in an external furnace is transferred to gas, usually air

which the working fluid of the cycle.

Internal combustion engine:

In this engine, the combustion of air and fuels take place inside the cylinder and are used as the direct motive

force. It can be classified into the following types:

1. According to the basic engine design- (a) Reciprocating engine (Use of cylinder piston arrangement), (b)

Rotary engine (Use of turbine)

2. According to the type of fuel used- (a) Petrol engine, (b) diesel engine, (c) gas engine (CNG, LPG), (d)

Alcohol engine (ethanol, methanol etc)

3. According to the number of strokes per cycle- (a) Four stroke and (b) Two stroke engine

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4. According to the method of igniting the fuel- (a) Spark ignition engine, (b) compression ignition engine

and (c) hot spot ignition engine

5. According to the working cycle- (a) Otto cycle (constant volume cycle) engine, (b) diesel cycle (constant

pressure cycle) engine, (c) dual combustion cycle (semi diesel cycle) engine.

6. According to the fuel supply and mixture preparation- (a) Carburetted type (fuel supplied through the

carburettor), (b) Injection type (fuel injected into inlet ports or inlet manifold, fuel injected into the

cylinder just before ignition).

7. According to the number of cylinder- (a) Single cylinder and (b) multi-cylinder engine

8. Method of cooling- water cooled or air cooled

9. Speed of the engine- Slow speed, medium speed and high speed engine

10. Cylinder arrangement-Vertical, horizontal, inline, V-type, radial, opposed cylinder or piston engines.

11. Valve or port design and location- Overhead (I head), side valve (L head); in two stroke engines: cross

scavenging, loop scavenging, uniflow scavenging.

12. Method governing- Hit and miss governed engines, quantitatively governed engines and qualitatively

governed engine

14. Application- Automotive engines for land transport, marine engines for propulsion of ships, aircraft

engines for aircraft propulsion, industrial engines, prime movers for electrical generators.

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=zKA4TYMgiqU

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-7008-

637-X.Pg No 32- 35.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : Advanced IC Engine

Unit : I – Spark Ignition Engines

Topic of Lecture: Mixture requirements

Introduction :

A heat engine is a device which transforms the chemical energy of a fuel into thermal energy and uses this

energy to produce mechanical work.

Prerequisite knowledge for Complete understanding and learning of Topic Gear terminology

3. Classification of Engine

4. Working Principle of SI Engine

Detailed content of the Lecture:

Mixture requirements for steady state operation:

Three main areas of steady state operation of automotive engine which require different air fuel ratio are

discussed below,

(a) Idling and low load:

 From no load to about 20% of rated power

 No load running mode is called idling condition

 Very low suction pressure give rise to back flow of exhaust gases and air leakage

Increases the amount of residual gases and hence increase the dilution effects

 Rich mixture i.e. F/A ratio 0.08 or A/F ratio 12.5:1 provide smooth operation of the engine

(b) Normal power range or cruising range:

 From about 20% to 75% of rated power

 Dilution by residual gases as well as leakage decreases, hence fuel economy is important

Consideration in this case

 Maximum fuel economy occurs at A/F ratio of 17:1 to 16.7:1

 Mixture ratios for best economy are very near to the mixture ratios for minimum emissions

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LECTURE HANDOUTS

Year/Sem : IV /

VII

MECH

(c) Maximum power range:

 From about 75% to 100% of rated power

 Mixture requirements for the maximum power is a rich mixture, of A/F about 14:1 or F/A 0.07.

 Rich mixture also prevents the overheating of exhaust valve at high load and inhibits detonation

 In multi-cylinder engine the A/F ratio are slightly lower

Mixture requirements for transient operation:

 Carburetor has to provide mixture for transient conditions under which speed, load, temperature, or

pressure change rapidly

 Evaporation of fuel may be incomplete in the transient condition, quantity of fuel may be increasing

and decreasing

(a) Starting and warm up requirements:

 Engine speed and temperature are low during the starting of the engine from cold

 During starting very rich mixture about 5 to 10 times the normal amount of petrol is sulpplied i.e.

F/A ratio 0.3 to 0.7 or A/F ratio 3:1 to 1.5:1

 Mixture ratio is progressively made leaner to avoid too rich evaporated fuel-air ratio during warm up

condition

 Too high volatility may form vapour bubbles in the carburettor and fuel lines particularly when

engine temperatures are high

 Too low volatility may cause the petrol to condense on the cylinder walls, diluting and removing the

lubricating oil film

(b) Acceleration requirements:

 Acceleration refer to an increase in engine speed resulting from the opening of the throttle

acceleration pump is used to provide additional fuel



Video Content / Details of website for further learning (if any): https://www.youtube.com/watch?v=ngXfCeGeeBg

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-7008-

637-X.Pg No 357- 366.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : Advanced IC Engine

Unit : I – Spark Ignition Engines

Topic of Lecture: Fuel injection systems

Introduction :

A heat engine is a device which transforms the chemical energy of a fuel into thermal energy and uses this

energy to produce mechanical work.

Prerequisite knowledge for Complete understanding and learning of Topic Gear terminology

5. Classification of Engine

6. Working Principle of SI Engine

Detailed content of the Lecture:

Petrol injection:

 To avoid above problem of modern carburettor, petrol injection is used like in diesel engine -petrol

injected during the suction stroke in the intake manifold at low pressure

 Injection timing is not much critical as like in diesel engine

Continuous injection and timed injection methods are used

1.12.1. Continuous injection:

 The fuel is sprayed at low pressure continuously into the air supply -amount of fuel is governed by

air throttle opening

 In supercharged engine, fuel injected in the form of multiple spray into the suction side of the

centrifugal compressor

 It provide efficient atomisation of fuel and uniform mixture strength to all cylinder.

higher volumetric efficiency.one fuel injection pump and one injector

1.12.2. Timed injection system:

 It is similar to high speed diesel engine

 The components are fuel feed or lift pump, fuel pump and distributor unit, fuel injection nozzles and

mixture controls

 mixture controls are automatic for all engine operating conditions

(i) Multiple plunger jerk pump system:

 Pump with separate plunger and high injection nozzle pressure for each cylinder

pressure is between 100 to 300 bar

 measured quantity of fuel for definite time and over definite period is delivered

(ii) Low pressure single pump and distributor system:

 Single plunger or gear pump supply fuel at low pressure to a rotating distributor -

pressure about 3.5 to 7 bar

(a) Lucas petrol injection system

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LECTURE HANDOUTS

Year/Sem : IV /

VII

MECH

 Firstly used in racing car

 Single distributor system with novel metering device Line pressure is maintained at 7 bar

 Metering distributor and control unit distributes the required amount of fuel at correct time

and interval

 Has shuttle arrangements for metering unit

 In aircraft engine two injectors and spark plug provided for direct injection of fuel in

combustion chamber

(B)Electronic fuel injection

Fuel delivery system

 Electrically driven fuel pump draws fuel from tanks to distribute Fuel and manifold pressure

kept constant by pressure regulator

Air induction system:

 Air flow meter generate voltage signal according to air flow

 Cold start magnetic injection valve give good fuel atomisation and also provide extra fuel during

warm up condition

Electronic control unit (ECU):

 Sensors for manifold pressure, engine speed and temperature at intake manifold -sensor

measures operating data from locations and transmitted electrically to ECU

Injection timing:

 Injected twice for every revolution of crank shaft

triggering of injectors

Video Content / Details of website for further learning (if any): https://www.youtube.com/watch?v=qId3Th6_a4U

Important Books/Journals for further learning including the page nos.: R.K.Rajbut, “Internal Combustion

Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-7008-637-X.Pg No 391- 393.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : Advanced IC Engine

Unit : I – Spark Ignition Engines

Topic of Lecture: Mono point, Multipoint & Direct injection

Introduction :

Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive

engines, by the means of an injector.

Prerequisite knowledge for Complete understanding and learning of Topic Gear terminology

1. Classification of Engine

2. Working Principle of SI Engine

Detailed content of the Lecture:

Single-point injection

 Single-point injection uses one injector in a throttle body mounted similarly to

a carburetor on an intake manifold. As in a carbureted induction system, the fuel is mixed

with the air before the inlet of the intake manifold.

 Single-point injection was a relatively low-cost way for automakers to reduce exhaust

emissions to comply with tightening regulations while providing better "driveability" (easy

starting, smooth running, freedom from hesitation) than could be obtained with a carburetor.

Many of the carburetor's supporting components - such as the air cleaner, intake manifold,

and fuel line routing - could be used with few or no changes. This postponed the redesign

and tooling costs of these components.

Multi-point injection

 Multi-point injection injects fuel into the intake ports just upstream of each cylinder's intake

valve, rather than at a central point within an intake manifold

 Typically, multi-point injected systems use multiple fuel injectors, but some systems such as the

GM central port injection use tubes with poppet valves fed by a central injector instead of

multiple injectors.

Injection schemes

 Manifold injected engines can use several injection schemes: continuous and intermittent

(simultaneous, batched, sequential, and cylinder-individual).

 In a continuous injection system, fuel flows at all times from the fuel injectors, but at a variable flow

rate. The most common automotive continuous injection system is the Bosch K-Jetronic, introduced

in 1974, and used until the mid-1990s by various car manufacturers.

 Intermittent injection systems can be sequential, in which injection is timed to coincide with each

cylinder's intake stroke; batched, in which fuel is injected to the cylinders in groups, without precise

synchronization to any particular cylinder's intake stroke; simultaneous, in which fuel is injected at

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LECTURE HANDOUTS

Year/Sem : IV /

VII

MECH

the same time to all the cylinders; or cylinder-individual, in which the engine control unit can adjust 
the injection for each cylinder individually.  
 
Internal mixture formation 
       In  an  engine  with  an  internal  mixture  formation  system,  air  and  fuel  are  mixed  only  inside  the 
combustion chamber. Therefore, only air is sucked into the engine during the intake stroke. The injection 
scheme is  always intermittent (either  sequential  or cylinder-individual).  There are two different types of 
internal mixture formation systems: indirect injection, and direct injection. 
Indirect injection 
 
 Air-cell chamber injection – the fuel injector (on the right) injects the fuel through the main 
combustion chamber into the air-cell chamber on the left. This is a special type of indirect injection 
and was very common in early American diesel engines. 
 Indirect injection as an internal mixture formation system (typical of Akroyd and Diesel engines); for 
the external mixture formation system that is sometimes called indirect injection (typical of Otto and 
Wankel engines), 
 In an indirect injected engine, there are two combustion chambers: a main combustion chamber, and 
a pre-chamber, that is connected to the main one. The fuel is injected only into the pre-chamber 
(where it begins to combust), and not directly into the main combustion chamber. Therefore, this 
principle is called indirect injection. There exist several slightly different indirect injection systems 
that have similar characteristics. All Akroyd (hot-bulb) engines, and some Diesel (compression 
ignition) engines use indirect injection. 
Direct injection 
 Direct injection means that an engine only has a single combustion chamber, and that the fuel is 
injected directly into this chamber. This can be done either with a blast of air (air-blast injection), or 
hydraulically. The latter method is far more common in automotive engines. 
 Typically, hydraulic direct injection systems spray the fuel into the air inside the cylinder or 
combustion chamber, but some systems spray the fuel against the combustion chamber walls (M-
System). Hydraulic direct injection can be achieved with a conventional, helix-controlled injection 
pump, unit injectors, or a sophisticated common-rail injection system.  
 The latter is the most common system in modern automotive engines. Direct injection is well-suited 
for a huge variety of fuels, including petrol (see petrol direct injection), and diesel fuel. 
 In a common rail system, the fuel from the fuel tank is supplied to the common header (called the 
accumulator). This fuel is then sent through tubing to the injectors, which inject it into the 
combustion chamber. The header has a high pressure relief valve to maintain the pressure in the 
header and return the excess fuel to the fuel tank. 

 The fuel is sprayed with the help of a nozzle that is opened and closed with a needle valve, operated

with a solenoid. When the solenoid is not activated, the spring forces the needle valve into the nozzle

passage and prevents the injection of fuel into the cylinder. The solenoid lifts the needle valve from

the valve seat, and fuel under pressure is sent in the engine cylinder.

 Third-generation common rail diesels use piezoelectric injectors for increased precision, with fuel

pressures up to 300 MPa or 44,000 lbf/in2

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=GlM9MHOX6iY

Important Books/Journals for further learning including the page nos.: R.K.Rajbut, “Internal Combustion

Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-7008-637-X.Pg No 425- 428.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : Advanced IC Engine

Unit : I – Spark Ignition Engines

Topic of Lecture: Stages of combustion

Introduction :

Combustion may be defined as a relatively rapid chemical combination of hydrogen and carbon in fuel with

oxygen in air resulting in liberation of energy in the form of heat

Prerequisite knowledge for Complete understanding and learning of Topic Gear terminology

1. Classification of Engine

2. Working Principle of SI Engine

Detailed content of the Lecture:

Combustion may be defined as a relatively rapid chemical combination of hydrogen and carbon in fuel

with oxygen in air resulting in liberation of energy in the form of heat. Following conditions are

necessary for combustion to take place: 1. The presence of combustible mixture 2. Some means to

initiate mixture 3. Stabilization and propagation of flame in Combustion Chamber In S I Engines,

carburetor supplies a combustible mixture of petrol and air and spark plug initiates combustion

Ignition Limits

Ignition of charge is only possible within certain limits of fuel-air ratio. Ignition limits

correspond approximately to those mixture ratios, at lean and rich ends of scale, where heat released by

spark is no longer sufficient to initiate combustion in neighboring unburnt mixture. For hydrocarbons

fuel the stoichiometric fuel air ratio is 1:15 and hence the fuel air ratio must be about 1:30 and 1:7.

Theories of Combustion in SI Engine

Combustion in SI engine may roughly is divided into two general types: Normal and Abnormal (knock

free or knocking). Theoretical diagram of pressure crank angle diagram is shown in figure below. (a  b) is

compression process, (b  c) is combustion process and (c   d) is an expansion process. In an ideal

cycle it can be seen from the diagram, the entire pressure rise during combustion takes place at constant

volume i.e., at TDC. However, in actual cycle this does not happen.

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LECTURE HANDOUTS

Year/Sem : IV /

VII

MECH

Richard Theory of Combustion:

Sir Ricardo, known as father of engine research describes the combustion process can be imagined as

if it is developing in two stages: 1. Growth and development of a self-propagating nucleus flame. (Ignition

lag) 2. Spread of flame through the combustion chamber

Video Content / Details of website for further learning (if any): https://www.youtube.com/watch?v=Y8l6AEquy94

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-7008-

637-X.Pg No 226- 234.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : Advanced IC Engine

Unit : I – Spark Ignition Engines

Topic of Lecture: Normal and Abnormal combustion

Introduction :

Combustion may be defined as a relatively rapid chemical combination of hydrogen and carbon in

fuel with oxygen in air resulting in liberation of energy in the form of heat.

Prerequisite knowledge for Complete understanding and learning of Topic Gear terminology

1. Classification of Engine

2. Working Principle of SI Engine

Detailed content of the Lecture:

Normal

combustion

 Spark-ignited flame moves steadily across the combustion chamber until the charge

is fully consumed.

 A combustion process which is initiated solely by a timed spark

and in which the flame front moves completely across the combustion chamber in

a uniform manner at a normal velocity.

Three Stage of Combustion:

 According to Ricardo, There are three stages of combustion in SI Engine as shown

 Ignition lag stage

 Flame propagation stage

 After burning stage

1. Ignition lag stage:

 There is a certain time interval between instant of spark and instant where there is a

noticeable rise in pressure due to combustion. This time lag is called IGNITION LAG.

Ignition lag is the time interval in the process of chemical reaction during which molecules

get heated up to self ignition temperature , get ignited and produce a self propagating nucleus

of flame. The ignition lag is generally expressed in terms of crank angle ( 1 ).

 The period of ignition lag is shown by path (a-b). Ignition lag is very small and lies between

0.00015 to 0.0002 seconds. An ignition lag of 0.002 seconds corresponds to 35 deg crank

rotation when the engine is running at 3000 RPM. Angle of advance increase with the speed.

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LECTURE HANDOUTS

Year/Sem : IV /

VII

MECH

This is a chemical process depending upon the nature of fuel, temperature and pressure,

proportions of exhaust gas and rate of oxidation or burning. 125

2. Flame propagation stage:

 Once the flame is formed at “b”, it should be self sustained and must be able to propagate

through the mixture. This is possible when the rate of heat generation by burning is

greater than heat lost by flame to surrounding. After the point “b”, the flame propagation

is abnormally low at the beginning as heat lost is more than heat generated. Therefore

pressure rise is also slow as mass of mixture burned is small.

 Therefore, it is necessary to provide angle of advance (30-35) degrees, if the peak

pressure to be attained (5-10) degrees after TDC. The time required for crank to rotate

through an angle (2) is known as combustion period during which propagation of flame

takes place.

3. After burning:

Combustion will not stop at point “c” but continue after attaining peak pressure and this

combustion is known as after burning. This generally happens when the rich mixture is supplied to

engine

Abnormal

combustion

 Fuel composition, engine design and operating parameters, combustion chamber

deposits may prevent occurring of the normal combustion process.A combustion

process in which a flame front may be started by hot combustion-chamber surfaces

either prior to or after spark ignition, or a process in which some part or all of

the charge may be consumed at extremely high rates

There are two types of abnormal combustion:

 Knock

 Surface ignition

Video Content / Details of website for further learning (if any):

Https://www.youtube.com/watch?v=Vtvy4NODK08

Important Books/Journals for further learning including the page nos.: R.K.Rajbut, “Internal Combustion

Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-7008-637-X.Pg No 201- 208.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : Advanced IC Engine

Unit : I – Spark Ignition Engines

Topic of Lecture: Knock

Introduction :

 Knock is the auto ignition of the portion of fuel, air and residual gas mixture

ahead of the advancing flame that produces a noise.

Prerequisite knowledge for Complete understanding and learning of Topic Gear terminology

1. Classification of Engine

2. Working Principle of SI Engine

Detailed content of the Lecture:

PHENOMENON OF KNOCKING IN SI ENGINE:

 Knocking is due to auto ignition of end portion of unburned charge in combustion chamber. As the

normal flame proceeds across the chamber, pressure and temperature of unburned charge increase

due to compression by burned portion of charge.

 This unburned compressed charge may auto ignite under certain temperature condition and release

the energy at a very rapid rate compared to normal combustion process in cylinder.

 This rapid release of energy during auto ignition causes a high-pressure differential in combustion

chamber and a high-pressure wave is released from auto ignition region.

 The motion of high-pressure compression waves inside the cylinder causes vibration of engine parts

and pinging noise and it is known as knocking or detonation. This pressure frequency or vibration

frequency in SI engine can be up to 5000 Cycles per second.

 Denotation is undesirable as it affects the engine performance and life, as it abruptly increases

sudden large amount of heat energy. It also put a limit on compression ratio at which engine can be

operated which directly affects the engine efficiency and output.

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LECTURE HANDOUTS

Year/Sem : IV /

VII

MECH

Auto ignition

A mixture of fuel and air can react spontaneously and produce heat by chemical reaction in the absence of

flame to initiate the combustion or self-ignition. This type of self-ignition in the absence of flame is known

as Auto-Ignition. The temperature at which the self-ignition takes place is known as self-igniting

temperature. The pressure and temperature abruptly increase due to auto-ignition because of sudden release

of chemical energy. This auto-ignition leads to abnormal combustion known as detonation which is

undesirable because its bad effect on the engine performance and life as it abruptly increases sudden large

amount of heat energy. In addition to this knocking puts a limit on the compression ratio at which an engine

can be operated which directly affects the engine efficiency and output.

Pre-ignition

Pre-ignition is the ignition of the homogeneous mixture of charge as it comes in contact with hot surfaces, in

the absence of spark. Auto ignition may overheat the spark plug and exhaust valve and it remains so hot that

its temperature is sufficient to ignite the charge in next cycle during the compression stroke before spark

occurs and this causes the pre-ignition of the charge. Pre-ignition is initiated by some overheated projecting

part such as the sparking plug electrodes, exhaust valve head, metal corners in the combustion chamber,

carbon deposits or protruding cylinder head gasket rim etc. pre-ignition is also caused by persistent

detonating pressure shockwaves scoring away the stagnant gases which normally protect the combustion

chamber walls. The resulting increased heat flow through the walls, raises the surface temperature of any

protruding poorly cooled part of the chamber, and this therefore provides a focal point for pre-ignition.

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=uWx1cXR7x_M

Important Books/Journals for further learning including the page nos.: R.K.Rajbut, “Internal Combustion

Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-7008-637-X.Pg No 208- 210.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : Advanced IC Engine

Unit : I – Spark Ignition Engines

Topic of Lecture: Factors affecting knock

Introduction :

A heat engine is a device which transforms the chemical energy of a fuel into thermal energy and uses

this energy to produce mechanical work.

Prerequisite knowledge for Complete understanding and learning of Topic Gear terminology

1. Classification of Engine

2. Working Principle of SI Engine

Detailed content of the Lecture:

Effects of Detonation

The harmful effects of detonation are as follows:

1. Noise and Roughness: Knocking produces a loud pulsating noise and pressure waves. These waves

which vibrates back and forth across the cylinder. The presence of vibratory motion causes crankshaft

vibrations and the engine runs rough.

2. Mechanical Damage:

(a) High pressure waves generated during knocking can increase rate of wear of parts of combustion

chamber. Sever erosion of piston crown( in a manner similar to that of 133 marine propeller blades by

capitation), cylinder head and pitting of inlet and outlet valves may result in complete wreckage of the

engine.

(b) Detonation is very dangerous in engines having high noise level. In small engines the knocking

noise is easily detected and the corrective measures can be taken but in aero-engines it is difficult to

detect knocking noise and hence corrective measures cannot be taken. Hence severe detonation may

persist for a long time which may ultimately result in complete wreckage of the piston.

3. Carbon deposits:

Detonation results in increased carbon deposits.

4. Increase in heat transfer: Knocking is accompanied by an increase in the rate of heat transfer to

the combustion chamber walls. The increase in heat transfer is due to two reasons: • The minor reason

is that the maximum temperature in a detonating engine is about 150°C higher than in a non-detonating

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LECTURE HANDOUTS

Year/Sem : IV /

VII

MECH

engine, due to rapid completion of combustion • The major reason for increased heat transfer is the

scouring away of protective layer of inactive stagnant gas on the cylinder walls due to pressure waves.

The inactive layer of gas normally reduces the heat transfer by protecting the combustion and piston

crown from direct contact with flame.

5. Decrease in power output and efficiency.

Due to increase in the rate of a detonating engine decreases.

6. Pre-ignition:

The increase in the rate of heat transfer to the walls has yet another effect. It may cause local

overheating, especially of the sparking plug, which may reach a temperature high enough to ignite the

charge before the passage of spark, thus causing pre-ignition. An engine detonating for a long period

would most probably lead to pre ignition and this is the real danger of detonation

EFFECT OF ENGINE OPERATING VARIABLES ON THE ENGINE KNOCKING DETONATION

The various engine variables affecting knocking can be classified as:

• Temperature factors

• Density factors

• Time factors

• Composition factors

(A) TEMPERATURE FACTORS Increasing the temperature of the unburned mixture increase the

possibility of knock in the SI engine We shall now discuss the effect of following engine

parameters on the temperature of the unburned mixture:

(B) RAISING THE COMPRESSION RATIO: Increasing the compression ratio increases both the

temperature and pressure (density of the unburned mixture). Increase in temperature reduces

the delay period of the end gas, which in turn increases the tendency to knock.

(C) SUPERCHARGING: It also increases both temperature and density, which increase the

knocking tendency of engine

(D) COOLANT TEMPERATURE: Delay period decreases with increase of coolant temperature ,

decreased delay period increase the tendency to knock

(E) TEMPERATURE OF THE CYLINDER AND COMBUSTION CHAMBER WALLS: The

temperature of the end gas depends on the design of combustion chamber. Sparking plug and

exhaust valve are two hottest parts in the combustion chamber and uneven temperature leads

to pre-ignition and hence the knocking.

(F) DENSITY FACTORS increasing the density of un burnt mixture will increase the possibility

of knock in the engine. The engine parameters that affect the density are as follows: Increased

compression ratio increase the density increasing the load opens the throttle valve more and

thus the density Supercharging increase the density of the mixture increasing the inlet

pressure increases the overall pressure during the cycle. The high-pressure end gas decreases

the delay period, which increase the tendency of knocking. 135 Advanced spark timing:

quantity of fuel burnt per cycle before and after TDC, position depends on spark timing. The

temperature of charge increases by increasing the spark advance and it increases with rate of

burning and does not allow sufficient time to the end mixture to dissipate the heat and increase

the knocking tendency.

(G) TIME FACTORS Increasing the time of exposure of the unburned mixture to auto-ignition

conditions increase the possibility of knock in SI engines. Flame travel distance: If the

distance of flame travel is more, then possibility of knocking is also more. This problem can

be solved by combustion chamber design, spark plug location and engine size. Compact

combustion chamber will have better anti-knock characteristics, since the flame travel and

combustion time will be shorter. Further, if the combustion chamber is highly turbulent, the

combustion rate is high and consequently combustion time is further reduced; this further

reduces the tendency to knock. Location of sparkplug: A spark plug that is centrally located in

the combustion chamber has minimum tendency to knock, as the flame travel is minimum.

The flame travel can be reduced by using two or more spark plugs. Location of exhaust valve:

The exhaust valve should be located close to the spark plug so that it is not in the end gas

region; otherwise, there will be a tendency to knock. Engine size: Large engines have a

greater knocking tendency because flame requires a longer time to travel across the

combustion chamber. In SI engine therefore , generally limited to 100mm Turbulence of

mixture decreasing the turbulence of the mixture decreases the flame speed and hence

increases the tendency to knock. Turbulence depends on the design of combustion chamber

and one engine speed.

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=w2TWPDdHYVo

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-

7008-637-X.Pg No 209 - 210.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : Advanced IC Engine

Unit : I – Spark Ignition Engines

Topic of Lecture: Combustion chambers

Introduction :

A heat engine is a device which transforms the chemical energy of a fuel into thermal energy and uses this

energy to produce mechanical work.

Prerequisite knowledge for Complete understanding and learning of Topic Gear terminology

7. Classification of Engine

8. Working Principle of SI Engine

Detailed content of the Lecture:

Design of Combustion Chambers

It involves

 Shape of combustion chamber

 Location of spark plug.

 Position of inlet and exhaust valves.

COMBUSTION CHAMBERS DESIGN PRINCIPLES.

1. High volumetric efficiency – largest possible inlet valve.

2. To prevent knock

* Minimum flame travel.

* Bore limited up to 100 mm in SIE. In CIE there is no limit.

* Proper location of spark plug, valves, shape of CC.

3. To reduce knock

* No hot surface in end gas portion.

* Exhaust valve should not be in end gas region and it should be near spark plug.

4. Small exhaust valve – high lift can be used.

5. Short combustion duration

 High flame velocity.

 Optimum turbulence.

 Suitable position of inlet valve.

 Streamlined passages.

6. Shape of combustion chambers -

largest mass of charge burns as soon as possible after ignition.

7. To get high BTE

 Minimum heat loss.

 Minimum S/V ratio in combustion zone.

 Hemispherical shape gives minimum S/V ratio and minimum air pollution.

8. In end gas region S/V ratio should be large

* Good cooling in knock zone.

* Quench space in end gas region.

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LECTURE HANDOUTS

Year/Sem : IV /

VII

MECH

9. Cooled exhaust valve head

* Hottest region in combustion chambers.

* High velocity water stream.

DIFFERENT

TYPES

OF

COMBUSTION

CHAMBERS

IN

SI

ENGINE

 T-head combustion chamber

 L-head combustion chamber

 I-head (or overhead valve) combustion chamber

 F-head combustion chamber

It may be noted that these chambers are designed to obtain the objectives namely:

 A high combustion rate at the start.

 A high surface-to-volume ratio near the end of burning.

 A rather centrally located spark plug.

i.T Head Type Combustion chambers

This was first introduced by Ford Motor Corporation in 1908. This design has

following disadvantages.

 Requires two cam shafts (for actuating the in-let valve and exhaust valve

separately) by two cams mounted on the two cam shafts.

 Very prone to detonation. There was violent detonation even at a

compression ratio of 4. This is because the average octane number in 1908

was about 40 -50.

ii.L Head Type Combustion chambers

It is a modification of the T-head type of combustion chamber. It provides the two

values on the same side of the cylinder, and the valves are operated through

tappet by a single camshaft. This was first introduced by Ford motor in 1910-30

and was quite popular for some time. This design has an advantage both from

manufacturing and maintenance point of view.

iii.Overhead valve or I head combustion chamber

The disappearance of the side valve or L-head design was inevitable at high

compression ratio of 8:1 because of the lack of space in the combustion chamber

to accommodate the valves. Diesel engines, with high compression ratios, invariably

used overhead valve design. Since 1950 or so mostly overhead valve combustion

chambers are used. This type of combustion chamber has both the inlet valve and

the exhaust valve located in the cylinder head. An overhead engine is superior to

side valve engine at high compression ratios.

The overhead valve engine is superior to side valve or L head engine at high

compression ratios, for the following reasons:

Fig.. Different Combustion Chambers

F- Head combustion chamber

In such a combustion chamber one valve is in head and other in the block. This

design is a compromise between L-head and I-head combustion chambers. One of

the most F head engines (wedge type) is the one used by the Rover Company

for several years. Another successful design of this type of chamber is that used

in Willeys jeeps.

Video Content / Details of website for further learning (if any):

https://unacademy.com/lesson/ic-engine-combustion-chambers-in-c-i-engine/4JQYJCLJ

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-7008-

637-X.Pg No 238 - 240.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : ADVANCED I.C ENGINES

Unit : 2 - COMPRESSION IGNITION ENGINES

Topic of Lecture : Diesel Fuel Injection Systems

Introduction:

The fuel is supplied through camshaft driven fuel pump. Fuel valve is also

connected with high pressure airline to inject into cylinder. In multi-stage compressor which supply air

at a pressure of about 60 to 70 bar

Prerequisite knowledge for Complete understanding and learning of Topic:

Air injection system, Solid injection system, Individual pump and injector or jerk pump

system, Common rail system 

Detailed content of the Lecture:

DIESEL INJECTION SYSTEM:

Requirements of diesel injection system:

 The fuel must introduce precisely defined period of cycle

 Amounts metered very accurately

 Rate of injection meet desired heat release pattern

 Quantities of fuel meet changing speed and load condition

 Good atomization of fuel

 Good spray pattern for rapid mixing of fuel and air

 No dribbling and after injection of fuel i.e. sharp injection

 Injection timing suits the speed and load requirements

 Distribution of fuel in multi

 Cylinder should uniform

 Weight, size and cost of fuel injection system should be less

Types of diesel injection system:

(a) Air injection system:

The fuel is supplied through camshaft driven fuel pump. Fuel valve is also connected with

high pressure airline to inject into cylinder. In multi-stage compressor which supply air at a pressure of

about 60 to 70 bar.

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LECTURE HANDOUTS

IV/VII

MECH

Fig. Air injection system

The blast air sweeps the fuel along with it. Good atomization results in good mixture formation and

hence high mean effective pressure. Here heavy and viscous fuels are used. The fuel pump require

small pressure. But it is complicated due to compressor arrangement and expensive.

(b) Solid injection system:

The fuel is directly injected to combustion chamber without primary atomization termed as solid

injection. It is also known as airless mechanical injection. 2 units are there, 1.Pressurise and

2.Atomising unit

3 different types which are described below,

(i) Individual pump and injector or jerk pump system:

The separate metering and compression pump is used for each cylinder. The reciprocating fuel pump

is used to meter and set the injection pressure of the fuel. The heavy gear arrangements which gives

jerking noise, hence name is given is jerk pump. The jerk pump is used for medium and high speed

diesel engines

Fig. . Individual pump and injector or jerk pump system

Fig. Unit injector

(ii) Common rail system:

The high pressure fuel pump delivers fuel to an accumulator whose pressure is constant. Here

plunger type of pump is used. The driving mechanism is not stressed with high pressure hence noise is

reduced. The common rail or pipe is connected in between accumulator and distributing elements. It is

separate metering and timing elements connected to automatic injector.

Fig. Common rail system

(iii) Distributor system:

The fuel pump pressurizes, meters and times the fuel supply to rotating distributor. The number of

injection strokes per cycle for the pump equals to the number of cylinder. One metering element which

ensure uniform distribution

Fig.. Distributor system

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=H28bE6gf5qQ

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-

7008-637-X.Pg No 226-228.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : ADVANCED I.C ENGINES

Unit : COMPRESSION IGNITION ENGINES

Topic of Lecture : Stages of combustion

Introduction:

Stages of combustion consists of our stages like Ignition delay period, Rapid or

uncontrolled or pre-mixed combustion phase, Controlled or diffusion combustion phase, After burning

or late combustion phase.

Prerequisite knowledge for Complete understanding and learning of Topic:

Ignition delay period, Rapid or uncontrolled or pre-mixed combustion

phase, Controlled or diffusion combustion phase, After burning or late combustion phase

Detailed content of the Lecture:

Stages of combustion in CI engine

1. Ignition delay period:

The period between the start of fuel injection into the combustion chamber and the start of combustion

is termed as ignition delay period. The start of combustion is determined from the change in slope on

p-θ diagram or from heat release analysis of the p-θ data, or from luminosity detector in experimental

conditions. Start of injection can be determined by a needle-lift indicator to record the time when

injector needle lifts off its seat. Start of combustion is more difficult to determine precisely. It is best

identified from the change in slope of heat release rate, determined from cylinder pressure data. In DI

engines ignition is well defined, in IDI engines ignition point is harder to identify

Both physical and chemical processes must take place before a significant fraction of the chemical

energy of the injected liquid is released.

Physical processes are fuel spray atomization, evaporation and mixing of fuel vapour with cylinder

air. Good atomization requires high fuel-injection pressure, small injector hole, optimum fuel viscosity,

high cylinder pressure (large divergence angle).

Rate of vaporization of the fuel droplets depends on droplet diameter, velocity, fuel volatility, pressure

and temperature of the air.

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LECTURE HANDOUTS

IV/VII

MECH

Fig.7. Stages of

combustion in CI

engine

Chemical processes similar to that described for auto ignition phenomenon in premixed fuel-air, only

more complex since heterogeneous reactions (reactions occurring on the liquid fuel drop surface) also

occur.

Chemical delay is more effective for the duration of the ignition delay period. Ignition

delay period is in the range of

0.6 to 3 ms for low-compression ratio DI diesel engines,

0.4 to 1 ms for high-compression ratio, turbocharged DI diesel engines, 0.6 to

1.5 ms for IDI diesel engines

2. Rapid or uncontrolled or pre-mixed combustion phase:

Combustion of the fuel which has mixed with air within flammability limits during ignition delay

period occurs rapidly in a few crank angle degrees - high heat release characteristics in this phase. If

the amount of fuel collected in the combustion chamber during the ignition delay is much - high heat

release rate results in a rapid pressure rise which causes the diesel knock.

For fuels with low cetane number, with long ignition delay, ignition occurs late in the expansion stroke

- incomplete combustion, reduced power output, poor fuel conversion efficiency. If the pressure

gradient is in the range 0.4 - 0.5 MPa/oCA, engine operation is not smooth and diesels knock starts.

This value should be in the range 0.2 to 0.3 MPa/oCA for smooth operation (max allowable value is 1.0

MPa/oCA) of the engine.

3. Controlled or diffusion combustion phase:

Once the fuel and air which is pre-mixed during the ignition delay is consumed, the burning rate (heat

release rate) is controlled by the rate at which mixture becomes available for burning. The rate of

burning in this phase is mainly controlled by the mixing process of fuel vapour and air. Liquid fuel

atomization, vaporization, pre flame chemical reactions also affect the rate of heat release.

Heat release rate sometimes reaches a second peak (which is lower in magnitude) and then decreases as

the phase progresses. Generally it is desirable to have the combustion process near the TDC for low

particulate (soot) emissions and high performance (and efficiency).

4. After burning or late combustion phase:

Heat release rate continues at a lower rate into the expansion stroke -there are several reasons for this: a

small fraction of the fuel may not yet burn, a fraction of the energy is present in soot and fuel-rich

combustion products and can be released. The cylinder charge is non-uniform and mixing during this

phase promotes more complete combustion and less dissociated product gases. Kinetics is slower.

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=H28bE6gf5qQ

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-

7008-637-X.Pg No 32- 35.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : ADVANCED I.C ENGINES

Unit : COMPRESSION IGNITION ENGINES

Topic of Lecture : Knocking

Introduction:

CI engine detonation occurs in the beginning of combustion. In CI engine the fuel and air are

imperfectly mixed and hence the rate of pressure rise is normally cause audible knock. Rate of

pressure rise may reach as high as 10 bar/ᵒCA-High engine vibration is the symptoms of knocking -no

pre-ignition or premature ignition as like SI engine.

Prerequisite knowledge for Complete understanding and learning of Topic:

Factors affecting knocking in SI engines, Methods Of Controling Diesel Knock

Detailed content of the Lecture:

knocking

Knocking is due to auto ignition of end portion of unburned charge in combustion chamber. As the

normal flame proceeds across the chamber, pressure and temperature of unburned charge increase due

to compression by burned portion of charge. This unburned compressed charge may auto ignite under

certain temperature condition and release the energy at a very rapid rate compared to normal

combustion process in cylinder. This rapid release of energy during auto ignition causes a high

pressure differential in combustion chamber and a high pressure wave is released from auto ignition

region. The motion of high pressure compression waves inside the cylinder causes vibration of engine

parts and pinging noise and it is known as knocking or detonation. This pressure frequency or vibration

frequency in SI engine can be up to 5000 Cycles per second. Denotation is undesirable as it affects the

engine performance and life, as it abruptly increases sudden large amount of heat energy. It also put a

limit on compression ratio at which engine can be operated which directly affects the engine efficiency

and output.

L - 12

LECTURE HANDOUTS

IV/VII

MECH

Detonation in CI engine

Auto ignition

A mixture of fuel and air can react spontaneously and produce heat by chemical reaction in the absence

of flame to initiate the combustion or self-ignition. This type of self-ignition in the absence of flame is

known as Auto-Ignition. The temperature at which the self-ignition takes place is known as self-

igniting temperature. The pressure and temperature abruptly increase due to auto-ignition because of

sudden release of chemical energy. This auto-ignition leads to abnormal combustion known as

detonation which is undesirable because its bad effect on the engine performance and life as it abruptly

increases sudden large amount of heat energy. In addition to this knocking puts a limit on the

compression ratio at which an engine can be operated which directly affects the engine efficiency and

output.

Pre-ignition

Pre-ignition is the ignition of the homogeneous mixture of charge as it comes in contact with hot

surfaces, in the absence of spark. Auto ignition may overheat the spark plug and exhaust valve and it

remains so hot that its temperature is sufficient to ignite the charge in next cycle during the

compression stroke before spark occurs and this causes the pre-ignition of the charge. Pre-ignition is

initiated by some overheated projecting part such as the sparking plug electrodes, exhaust valve head,

metal corners in the combustion chamber, carbon deposits or protruding cylinder head gasket rim etc.

pre-ignition is also caused by persistent detonating pressure shockwaves scoring away the stagnant

gases which normally protect the combustion chamber walls. The resulting increased heat flow through

the walls, raises the surface temperature of any protruding poorly cooled part of the chamber, and this

therefore provides a focal point for pre-ignition.

Effects of Pre-ignition

-It increase the tendency of denotation in the engine

-It increases heat transfer to cylinder walls because high temperature gas remains in contact with for a

longer time

-Pre-ignition in a single cylinder will reduce the speed and power output

-Pre-ignition may cause seizer in the multi-cylinder engines, only if only cylinders have pre-ignition

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=H28bE6gf5qQ

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-

7008-637-X.Pg No 228-230.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : ADVANCED I.C ENGINES

Unit : COMPRESSION IGNITION ENGINES

Topic of Lecture : Factors affecting knock

Introduction:

CI engine detonation occurs in the beginning of combustion. In CI engine the fuel and air are

imperfectly mixed and hence the rate of pressure rise is normally cause audible knock. Rate of

pressure rise may reach as high as 10 bar/ᵒCA-High engine vibration is the symptoms of knocking -no

pre-ignition or premature ignition as like SI engine.

Prerequisite knowledge for Complete understanding and learning of Topic:

Factors affecting knocking in SI engines,

Methods Of Controling Diesel Knock

Detailed content of the Lecture:

FACTORS

AFFECTING

KNOCKING

IN

SI

ENGINES

CI engine detonation occurs in the beginning of combustion. In CI engine the fuel and air are

imperfectly mixed and hence the rate of pressure rise is normally cause audible knock. Rate of

pressure rise may reach as high as 10 bar/ᵒCA-High engine vibration is the symptoms of knocking -no

pre-ignition or premature ignition as like SI engine.

Knocking is violet gas vibration and audible sound produced by extreme pressure is going

through differentials leading to the very rapid rise during the early part of uncontrolled to the

second phase of combustion.

In C.I. engines the injection process takes place over a definite interval of time.

Consequently, as the first few droplets injected are passing through the ignition lag

period, additional droplets are being injected into the chamber. If the ignition delay

is longer, the actual burning of the first few droplets is delayed and a greater

quantity of fuel droplets gets accumulated in the chamber. When the actual burning

commences, the additional fuel can cause too rapid a rate of pressure rise, as

shown on pressure crank angle diagram above, resulting in Jamming of forces

against the piston (as if struck by a hammer) and rough engine operation. If the

ignition delay is quite long, so much fuel can accumulate that the rate of pressure

rise is almost instantaneous. Such, a situation produces extreme pressure

differentials and violent gas vibration known as knocking (diesel knock), and is

L - 13

LECTURE HANDOUTS

IV/VII

MECH

evidenced by audible knock. The phenomenon is similar to that in the SI engine.

However, in SI Engine knocking occurs near the end of combustion whereas in CI

engine, knocking the occurs near the beginning of combustion.

Delay

period

is

directly

Knocking

in

CI

engine.

An

extensive

delay

period

can

be

due

to

following

factors:

A low compression ratio permitting only a marginal self-ignition temperature to be

reached.

 A low combustion pressure due to worn out piston, rings and bad valves

 Low cetane number of fuel

 Poorly atomized fuel spray preventing early combustion

 Coarse droplet formation due to malfunctioning of injector parts like spring

 Low intake temperature and pressure of air

METHODS

OF

CONTROLING

DIESEL

KNOCK

We have discussed the factors which are responsible for the detonation in the

previous sections. If these factors are controlled, then the detonation can be

avoided.

Using a better fuel:

Higher Cetene number fuel has lower delay period and reduces knocking tendency.

Controlling the Rate of Fuel Supply:

By injecting less fuel in the beginning and then more fuel amount in the

combustion chamber detonation can be controlled to a certain extent. Cam shape

of suitable profile can be designed for this purpose.

Knock reducing fuel injector:

This type of injector avoids the sudden increase in pressure inside the combustion

chamber because of accumulated fuel. This can be done by arranging the injector

so that only small amount of fuel is injected first. This can be achieved by using

two or more injectors arranging in out of phase.

By using Ignition accelerators:

C N number can be increased by adding chemical called dopes. The two chemical

dopes are used are ethyl-nitrate and amyle ”nitrate in concentration of 8.8

gm/Litre and 7.7 gm/Litre. But these two increase the NOx emissions.

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=H28bE6gf5qQ

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-

7008-637-X.Pg No 236-238.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : ADVANCED I.C ENGINES

Unit : COMPRESSION IGNITION ENGINES

Topic of Lecture : Direct and Indirect injection systems

Introduction:

An indirect injection diesel engine delivers fuel into a chamber of

the combustion chamber, called a pre-chamber or ante-chamber, where

combustion begins and then spreads into the main combustion chamber,

assisted by turbulence created in the chamber.

Prerequisite knowledge for Complete understanding and learning of Topic:

Direct and Indirect Injection Systems

Detailed content of the Lecture:

DIRECT

AND

INDIRECT

INJECTION

SYSTEMS

1. Direct injection diesel engines have injectors mounted at the top of the

combustion chamber.

2. The injectors are activated using one of two methods - hydraulic pressure

from the fuel pump, or an electronic signal from an engine controller.

3. Hydraulic pressure activated injectors can produce harsh engine noise.

4. Fuel consumption is about 15 to 20% lower than indirect injection diesels.

5. The extra noise is generally not a problem for industrial uses of the engine,

but for automotive usage, buyers have to decide whether or not the

increased fuel efficiency would compensate for the extra noise.

6.Electronic control of the fuel injection transformed the direct injection engine

by allowing much greater control over the combustion.

L - 14

LECTURE HANDOUTS

IV/VII

MECH

Fig.Direct

and

Indirect

Injection

Systems

INDIRECT INJECTION DIESEL ENGINE

1. An indirect injection diesel engine delivers fuel into a chamber off

the combustion chamber, called a pre-chamber or ante-chamber, where

combustion begins and then spreads into the main combustion chamber,

assisted by turbulence created in the chamber.

2. This system allows for a smoother, quieter running engine, and because

combustion is assisted by turbulence, injector pressures can be lower, about

100 bar (10 MPa; 1,500 psi), using a single orifice tapered jet injector.

3. Mechanical injection systems allowed high-speed running suitable for road

vehicles (typically up to speeds of around 4,000 rpm).

4. The pre-chamber had the disadvantage of increasing heat loss to the

engine's cooling system, and restricting the combustion burn, which reduced

the efficiency by 5”10%.[35] Indirect injection engines are cheaper to build

and it is easier to produce smooth, quiet-running vehicles with a simple

mechanical system.

5.In road-going vehicles most prefer the greater efficiency and better

controlled emission levels of direct injection.

6. Indirect injection diesels can still be found in the many ATV diesel applications.

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=H28bE6gf5qQ

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-

7008-637-X.Pg No 236-238.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : ADVANCED I.C ENGINES

Unit : COMPRESSION IGNITION ENGINES

Topic of Lecture : Combustion chambers

Introduction:

An indirect injection diesel engine delivers fuel into a chamber of

the combustion chamber, called a pre-chamber or ante-chamber, where

combustion begins and then spreads into the main combustion chamber,

assisted by turbulence created in the chamber.

Prerequisite knowledge for Complete understanding and learning of Topic:

Direct Injection Chambers,

Indirect Injection Combustion Chambers,

Detailed content of the Lecture:

TYPES

OF

COMBUSTION

CHAMBERS-

CI

Engines

CI engine combustion chambers are classified into two categories:

1.

OPEN

INJECTION

(DI)

TYPE:

This type of combustion chamber is also called an Open combustion chamber. In

this type the entire volume of combustion chamber is located in the main cylinder

and the fuel is injected into this volume.

2.

INDIRECT

INJECTION

(IDI)

TYPE:

in this type of combustion chambers, the combustion space is divided into two

parts, one part in the main cylinder and the other part in the cylinder head. The

fuel ”injection is effected usually into the part of chamber located in the cylinder

head. These chambers are classified

1.DIRECT

INJECTION

CHAMBERS

–

OPEN

COMBUSTION

CHAMBERS

L - 15

LECTURE HANDOUTS

IV/VII

MECH

Shallow Depth Chamber:

In shallow depth chamber the depth of the cavity provided in the piston is quite

small. This chamber is usually adopted for large engines running at low speeds.

Since the cavity diameter is very large, the squish is negligible.

Hemispherical Chamber:

This chamber also gives small squish. However, the depth to diameter ratio for a

cylindrical chamber can be varied to give any desired squish to give better

performance.

Fig.9 Different combustion chambers

Cylindrical Chamber:

This design was attempted in recent diesel engines. This is a modification of the

cylindrical chamber in the form of a truncated cone with base angle of 30°. The

swirl was produced by masking the valve for nearly 1800 of circumference. Squish

can also be varied by varying the depth.

Toroidal Chamber:

The idea behind this shape is to provide a powerful squish along with the air

movement, similar to that of the familiar smoke ring, within the toroidalchamber.

Due to powerful squish the mask needed on inlet valve is small and there is

better utilisation of oxygen. The cone angle of spray for this type of chamber is

150° to 160°.

2. INDIRECT

INJECTION

COMBUSTION

CHAMBERS

(a)

Ricardo’s Swirl Chamber:

Swirl chamber consists of a spherical shaped chamber separated from the engine

cylinder and located in the cylinder head. In to this chamber, about 50% of the

air is transferred during the compressionstroke. A throat connects the chamber to

the cylinder which enters the chamber in a tangential direction so that the air

coming into this chamber is given a strong rotary movement inside the swirl

chamber and after combustion, the products rush back into the cylinder through

same throat at much higher velocity. The use of single hole of larger diameter for

the fuel spray nozzle is often important consideration for the choice of swirl

chamber engine.

Fig . Ricardo’s Swirl Chamber:

(a)

Pre Combustion Chamber

Typical pre-combustion chamber consists of an anti-chamber connected to the main

chamber through a number of small holes (compared to a relatively large passage

in the swirl chamber). The pre-combustion chamber is located in the cylinder head

and its volume accounts for about 40% of the total combustion, space. During the

compression stroke the piston forces the air into the pre-combustion chamber. The

fuel is injected into the pre-chamber and the combustion is initiated. The resulting

pressure rise forces the flaming droplets together with some air and their

combustion products to rush out into the main cylinder at high velocity through the

small holes.

Fig.

Pre Combustion Chamber

(a)

Energy cell:

The ‘energy cell’ is more complex than the precombustion chamber. As the piston

moves up on the compression stroke, some of the air is forced into the major and

minor chambers of the energy cell. When the fuel is injected through the pintle

type nozzle, part of the fuel passes across the main combustion chamber and

enters the minor cell, where it is mixed with the entering air. Combustion first

commences in the main combustion chamber where the temperatures higher, but

the rate of burning is slower in this location, due to insufficient mixing of the fuel

and air. The burning in the minor cell is slower at the start, but due to better

mixing, progresses at a more rapid rate. The pressure built up in the minor cell ,

therefore , force the burning gases out into the main chamber, thereby creating

added turbulence and producing better combustion in the this chamber.

Fig. Energy cell:

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=H28bE6gf5qQ

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-7008-637-X.Pg No

239-240.

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(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : ADVANCED I.C ENGINES

Unit : COMPRESSION IGNITION ENGINES

Topic of Lecture : Fuel Spray behavior

Introduction:

 Depending on the mechanism to characterize, diesel spray can be analyzed in a macroscopic or

microscopic point of view.

 With the purpose of understanding in detail this process, the various physical parameters

involved

 during the transition of a pulsed diesel spray will be expressed in this chapter,

 however it is essential to know the systems that make possible for an injection process to take

place

Prerequisite knowledge for Complete understanding and learning of Topic:

Diesel spray characteristics, Atomization

Detailed content of the Lecture:

Diesel spray characteristics

 Depending on the mechanism to characterize, diesel spray can be analyzed in a macroscopic or

microscopic point of view. With the purpose of understanding in detail this process, the various

physical parameters involved during the transition of a pulsed diesel spray will be expressed in

this chapter.

 however it is essential to know the systems that make possible for an injection process to take

place. These are the injection nozzle, active fluid to inject (liquid), and the working fluid on

which the liquid is injected, as seen in

figure 1.

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LECTURE HANDOUTS

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Fig. Meaningful variables of the injection process

Reynolds Number: Density and kinematic viscosity must be particularized for liquid or gas,

furthermore these properties can be evaluated for intermediate conditions between both fluid film

conditions. These parameters can be divided into two groups:

1. External flow parameters (relation of densities, Weber number, Taylor parameter), these

parameters control the interaction between the liquid spray and the surrounding atmosphere.

2. Internal flow parameters (Reynolds number, cavitation parameter, length/diameter relation,

nozzle radius entrance/diameter relation, discharge coefficient): these parameters control the

interaction between the liquid and the nozzle.

ATOMIZATION

 Disintegration of fuel stream issuing from the injector nozzle into droplets of different sizes.

Disintegration presents large surface and quicker heating and vaporization of droplets. Caused

by friction between stream of fuel and air in Combustion chamber. Previous studies have shown

that a spray penetration overcomes that of a single droplet, due to the momentum that the

droplets.

 Located in the front of the spray experiment, accelerating the surrounding working fluid,

causing the next droplets that make it to the front of the spray an instant of time later to have

less aerodynamic resistance. We must emphasize that diesel fuel sprays tend to be of the

compact type, which causes them to have large penetrations.

 Several researchers have studied the front penetration and have found a series of correlations

that allow us to establish the main variables that affect or favour the penetration of a pulsed

diesel spray. The following are some of the most relevant. From the theory of gaseous sprays,

was one of the pioneers in the study of spray phenomena.

 The author proposed an experimentally adjusted correlation which is applicable to pulsed

diesel sprays; this correlation was the compared by with other correlations, finding certain

discrepancies between them. However, this correlation is considered to be applicable in a

general form to diesel sprays

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=H28bE6gf5qQ

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-

7008-637-X.Pg No 287-290.

Course Faculty

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MUTHAYAMMAL ENGINEERING COLLEGE

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Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : ADVANCED I.C ENGINES

Unit : COMPRESSION IGNITION ENGINES

Topic of Lecture : Spray structure and spray penetration and Air Motion

Introduction:

 The injection front penetration (S) is defined as the total distance covered by the spray in a

control volume, and it’s determined by the equilibrium of two factors,

 first the momentum quantity with which the fluid is injected and

 second, the resistance that the idle fluid presents in the control volume, normally a gas

Prerequisite knowledge for Complete understanding and learning of Topic:

1. Spray tip penetration,

2. Spray angle,

3. Break up length

Detailed content of the Lecture:

1. Spray tip penetration

2. Spray angle

3. Air Motion

Physical parameter of a diesel spray

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LECTURE HANDOUTS

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MECH

1. Front Penetration

o The injection front penetration (S) is defined as the total distance covered by the spray

in a control volume, and it’s determined by the equilibrium of two factors, first the

momentum quantity with which the fluid is injected and second, the resistance that the

idle fluid presents in the control volume, normally a gas.

 Due to friction effects, the liquids kinetic energy is transferred progressively to the working

fluid. This energy will decrease continuously until the movement of the droplets depends solely

on the movement of the working fluid inside the control volume.

 Previous studies have shown that a spray penetration overcomes that of a single droplet, due to

the momentum that the droplets.

 located in the front of the spray experiment, accelerating the surrounding working fluid, causing

the next droplets that make it to the front of the spray an instant of time later to have less

aerodynamic resistance.

 We must emphasise that diesel fuel sprays tend to be of the compact type, which causes them to

have large penetrations.Several researchers have studied the front penetration and have found a

series of correlations that allow us to establish the main variables that affect or favour the

penetration of a pulsed diesel spray.

 The following are some of the most relevant. From the theory of gaseous sprays, was one of the

pioneers in the study of spray phenomena. The author proposed an experimentally adjusted

correlation which is applicable to pulsed diesel sprays; this correlation was the compared by

with other correlations, finding certain discrepancies between them.

 However, this correlation is considered to be applicable in a general form to diesel sprays

2. Cone angle

 The cone angle is defined as the angle formed by two straight lines that stat from the exit orifice

of the nozzle and tangent to the spray outline (sprays morphology) in a determined distance.

 The angle in a diesel spray is formed by two straight lines that are in contact with the spray’s

outline and at a distance equivalent to 60 times de exit diameter of the nozzles orifice.

 This angle usually is between 5 and 30 degrees. This determines greatly the fuels macroscopic

distribution in the combustion chamber. In one hand, the increase in angle decreases the

penetration and can cause interference between sprays (when sprays are injected using multi -

orifice nozzles) in the same chamber favouring the merging of droplets.

 On the other hand, an excessive penetration is favoured when the angle decreases lower than

certain values, causing the spray to collide with the piston bowl or the combustion chamber.

 In previous studies there have been a series of proposals to determine the cone angle, some of

the most important are as follows:

3. Air Motion

 The liquid length of the spray is a very important characteristic to define the behaviour of the

spray in the combustion chamber. This zone of the spray is also called continuous or stationary

and it is understood as being from the nozzle exit to the point were the separation of the first

droplets occur.

 To define this zone the use of diverse measurements methods and techniques is of vital

importance. In the literature we find some of the most useful measurement methods and

techniques in the analysis of the liquid length

 To analyze the internal structure of the spray, identified two zones inside the atomizing regime,

the zone of the incomplete spray and the zone of the complete spray. Figure shows structure in

a general way.

 The difference between them is due to the fact that with the incomplete sprays the

disintegration of the surface of the spray begins at a certain distance from the point of the

nozzle of the injector, indicating a distance Lc, while in the case of the incomplete sprays

distance Lc is nearly cero and Lb is maintained virtually constant on increasing speed.

 Furthermore show that cavitation greatly favours the atomization process in the complete spray

regime.

 To define liquid length a series of expressions have been proposed which have been suggested

in specific conditions according to each case and among the most relevant the following can be

cited:

Fig. Internal structure of complete and incomplete spray

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=H28bE6gf5qQ

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-

7008-637-X.Pg No 241-243.

Course Faculty

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(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : ADVANCED I.C ENGINES

Unit : COMPRESSION IGNITION ENGINES

Topic of Lecture: Introduction to Turbo charging.

Introduction:

A turbocharger or turbo is a forced induction device used to allow more power to

be produced for an engine of a given size. A turbocharged engine can be more

powerful and efficient than a naturally aspirated engine because the turbine forces

more air, and proportionately more fuel, into the combustion chamber than

atmospheric pressure alone.

Prerequisite knowledge for Complete understanding and learning of Topic:

1. Turbo Charger

2. Working Principle

3. Component

Detailed content of the Lecture:

Turbocharger

A turbocharger or turbo is a forced induction device used to allow more power to

be produced for an engine of a given size. A turbocharged engine can be more

powerful and efficient than a naturally aspirated engine because the turbine forces

more air, and proportionately more fuel, into the combustion chamber than

atmospheric pressure alone.

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LECTURE HANDOUTS

IV/VII

MECH

Fig. Turbocharger

Working

principle

 a

turbocharger

is a small radial fan pump driven by the energy of the exhaust

gases of an engine. A

turbocharger

consists of a turbine and a compressor on a

shared shaft. The turbine section of a turbocharger is a heat engine in itself.

 It converts the heat energy from the exhaust to power, which then drives the

compressor, compressing ambient air and delivering it to the air intake manifold of

 the engine at higher pressure, resulting in a greater mass of air entering each

cylinder.

 In some instances, compressed air is routed through an intercooler before

introduction to the intake manifold. Because a turbocharger is a heat engine, and

is converting otherwise wasted exhaust heat to power, it compresses the inlet air

to the engine more efficiently than a supercharger.

Components

 The turbocharger has four main components.

 The

turbine

(almost always a radial

turbine) and impeller/compressor wheels are each contained within their own folded

conical housing on opposite sides of the third component, the centre housing/hub

rotating assembly (CHRA).

 The housings fitted around the

compressor

impeller

and

turbine

collect and direct

the gas flow through the wheels as they spin. The size and shape can dictate

some performance characteristics of the overall turbocharger.

 turbocharger assembly will be available from the manufacturer with multiple housing

choices for the turbine and sometimes the compressor cover as well.

 the designer of the engine system to tailor the compromises between performance,

response, and efficiency to application or preference.

 valve-operated exhaust gas inlets, a smaller sharper angled one for quick response

and a larger less angled one for peak performance.

 The

turbine

and

impeller

wheel

sizes also dictate the amount of air or exhaust that

can be flowed through the system, and the relative efficiency at which they

operate.

 Generally, the larger the turbine wheel and compressor wheel, the larger

the flow capacity. Measurements and shapes can vary, as well as curvature and

number of blades on the wheels. Variable geometry turbochargers are further

developments of these ideas.

 The

centre

hub

rotating assembly (CHRA) houses the shaft which connects the

compressor impeller and turbine. It also must contain a bearing system to suspend

the shaft, allowing it to rotate at very high speed with minimal friction.

 instance, in automotive applications the CHRA typically uses a thrust bearing or ball

bearing lubricated by a constant supply of pressurized engine oil.

 also be considered "water cooled" by having an entry and exit point for engine

coolant to be cycled.

 Water cooled models allow engine coolant to be used to

keep the lubricating oil cooler, avoiding possible oil coking from the extreme heat

found in the turbine. The development of air-foil bearings has removed this risk.

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=H28bE6gf5qQ

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-7008-637-X.Pg No

520-526.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : ADVANCED I.C ENGINES

Unit : 3- POLLUTANT FORMATION AND CONTROL

Topic of Lecture : Pollutant Sources

Introduction:

Internal combustion engines (ICE) operate by burning fossil fuel derivatives. Exhaust

Emissions are their major contribution to environmental pollution.

Prerequisite knowledge for Complete understanding and learning of Topic:

Typical emissions

contain primary greenhouse gases – carbon dioxide (CO2), methane (CH4) and nitrous

oxide (N2O). All criteria pollutants – carbon monoxide (CO), total nitrogen oxides (NO

x), sulfur dioxide (SO2), non-methane volatile organic compounds (NMVOC) and

particulate matter (PM) are the other major components

Detailed content of the Lecture:

Internal Combustion Engines.

 ICE may be classified by different criteria. For instance, - according to fuel type, to power, to

ignition type and so on. An appropriate classification from the point of view of combustion

chemistry and air pollution will divide them into two major groups.

 The first group includes engines in which combustion is performed periodically in a chamber of

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LECTURE HANDOUTS

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MECH

changing volume (i. e. reciprocating piston engines).

 In the second group combustion takes place continuously (steady flow) in a chamber of constant

volume.

 The first group may be further divided into spark ignition (SI) and compression ignition (CI)

engines, although there are engines combining both principles.

 SI engines may be classified as two stroke and four stroke engines, CI engines – as direct and

indirect injection engines.

 The second group includes the jet engines, which may use a gas turbine, liquid fuel, air

as oxidation agent and a turbo compressor (aircraft jet engines), and the rocket jet engines,

which have chemical agents as fuels and oxidizers.

 Details of combustion systems, combustion processes, efficiencies, Another useful distinction

between internal combustion engines is the fact that only in SI engines the fuel is evaporated and

mixed with the oxidizing agent before the ignition takes place. In other designs, the fuel is

sprayed in the combustion chamber, in the form of drops of different size.

 It is not the purpose of this chapter to describe the organization of the combustion

Processes in the different engines. Its main task is rather to compare the main groups

etc. can be found in Pollution Control through Efficient Combustion Technology. Have the

important advantages of lower weight and cost per unit of power output.

 They are widely used in small motorcycles, as outboard motors and other small power

equipment.

 The main pollutants from four-stroke gasoline engines are hydrocarbons, CO and nitrogen

oxides. They are contained in exhaust emissions, but hydrocarbons are contributed both with the

exhaust, and with the evaporative emissions.

 Particulate matter is usually negligible and is produced mainly from oil components brought in

the combustion chamber by the piston. Sulfur oxides are typically low and for some time were

not considered a problem. New regulations restrict drastically sulfur in gasoline, because of

reconsidering its influence on catalysts.

SI/CI

ENGINE

EMISSIONS

1. Unburned Hydro Carbons

2. Carbon monoxide

3. Oxides of nitrogen

4. Oxides of sulphur and

5. Particulates including smoke

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=AVBjNCtqe4M&list=PL215741C530D11AFB&index=5&t=0s

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-

7008-637-X.Pg No 612-614.

Course Faculty

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MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : ADVANCED I.C ENGINES

Unit : 3 - POLLUTANT FORMATION AND CONTROL

Topic of Lecture : Formation of Carbon Monoxide

Introduction:

The nitric oxide formation during the combustion process is the result of

group of elementary reaction involving the nitrogen and oxygen molecules. Different

mechanism proposed is discussed below.

Prerequisite knowledge for Complete understanding and learning of Topic:

 Mechanism of NO formation

 Simple reaction between N2 and O2

 Zeldovich Chai Reaction mechanism

Detailed content of the Lecture:

Formation

of

NOX,

HC/CO

mechanism

Mechanism

of

NO

formation:

The nitric oxide formation during the combustion process is the result of

group of elementary reaction involving the nitrogen and oxygen molecules. Different

mechanism proposed is discussed below.

a.

Simple

reaction

between

N

2

and

O

2

N2 + O2  2 NO

This mechanism proposed by Eyzat and Guibet predicts NO concentrations

much lower that those measured in I.C engines. According to this mechanism, the

formation process is too slow for NO to reach equilibrium at peak temperatures and

pressures in the cylinders.

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LECTURE HANDOUTS

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MECH

b.

Zeldovich

Chai

Reaction

mechanism:

O2 2 O------------- (1)

O + N2  NO + N ------(2)

N + O2 NO + O ------(3)

The chain reactions are initiated by the equation (2) by the atomic oxygen,

formed in equation (1) from the dissociation of oxygen molecules at the high

temperatures reached in the combustion process. Oxygen atoms react with nitrogen

molecules and produces NO and nitrogen atoms. In the equation (3) the nitrogen

atoms react with oxygen molecule to form nitric oxide and atomic oxygen.

According to this mechanism nitrogen atoms do not start the chain reaction

because their equilibrium concentration during the combustion process is relatively

low compared to that of atomic oxygen. Experiments have shown that equilibrium

concentrations of both oxygen atoms and nitric oxide molecules increase with

temperature and with leaning of mixtures. It has also been observed that NO

formed at the maximum cycle temperature does not decompose even during the

expansion stroke when the gas temperature decreases.

In general it can be expected that higher temperature would promote the

formation of NO by speeding the formation reactions. Ample O2 supplies would also

increase the formation of NO. The NO levels would be low in fuel rich operations,

i.e. A/F 15, since there is little O2 left to react with N2 after the hydrocarbons

had reacted.

The maximum NO levels are formed with AFR about 10 percent above

stoichiometric. More air than this reduces the peak temperature, since excess air

must be heated from energy released during combustion and the NO concentration

fall off even with additional oxygen.

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=AVBjNCtqe4M&list=PL215741C530D11AFB&index=5&t=0s

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-

7008-637-X.Pg No 615-617.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : ADVANCED I.C ENGINES

Unit : 3 - POLLUTANT FORMATION AND CONTROL

Topic of Lecture : Unburned hydrocarbon (HC)

Introduction:

Hydrocarbon exhaust emission may arise from three sources as,

a. Wall quenching

b. Incomplete combustion of charge

c. Exhaust scavenging in 2-stroke engines

Prerequisite knowledge for Complete understanding and learning of Topic:

Because of the cooling, there is a cold zone next to the cooled combustion

chamber walls. This region is called the quench zone. Because of the low

temperature, the fuel-air mixture fails to burn and remains unburned.



Detailed content of the Lecture:

Unburned hydrocarbon (HC) exhaust emission may arise from three sources as,

a. Wall quenching

b. Incomplete combustion of charge

c. Exhaust scavenging in 2-stroke engines

In an automotive type 4-stroke cycle engine, wall quenching is the predominant

source of exhaust hydrocarbon under most operating conditions.

The quenching of flame near the combustion chamber walls is known as wall

quenching. This is a combustion phenomenon which arises when the flame tries to

propagate in the vicinity of a wall. Normally the effect of the wall is a slowing

down or stopping of the reaction.

Because of the cooling, there is a cold zone next to the cooled combustion

chamber walls. This region is called the quench zone. Because of the low

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LECTURE HANDOUTS

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MECH

temperature, the fuel-air mixture fails to burn and remains unburned.

Due to this, the exhaust gas shows a marked variation in HC emission.

The first gas that exits is from near the valve and is relatively cool. Due to this it

is rich in HC. The next part of gas that comes is from the hot combustion

chamber and hence a low HC concentration. The last part of the gas that exits is

scrapped off the cool cylinder wall and is relatively cool. Therefore it is also rich

in HC emission.

Video Content / Details of website for further learning (if any):

https://www.youtube.com/watch?v=AVBjNCtqe4M&list=PL215741C530D11AFB&index=5&t=0s

Important Books/Journals for further learning including the page nos.:

R.K.Rajbut, “Internal Combustion Engines”, Lakshmi Publications of India LTD,Chennai, ISBN 81-

7008-637-X.Pg No 618-620.

Course Faculty

Verified by HOD

MUTHAYAMMAL ENGINEERING COLLEGE

(An Autonomous Institution)

(Approved by AICTE, New Delhi, Accredited by NAAC & Affiliated to Anna University)

Rasipuram - 637 408, Namakkal Dist., Tamil Nadu

Course Name : ADVANCED I.C ENGINES

Unit : 3- POLLUTANT FORMATION AND CONTROL

Topic of Lecture : Oxides of Nitrogen (NO)

Introduction:

The nitric oxide formation during the combustion process is the result of

group of elementary reaction involving the nitrogen and oxygen molecules.

Different mechanism proposed is discussed below

Prerequisite knowledge for Complete understanding and learning of Topic:

N2 + O2  2 NO

This mechanism proposed by Eyzat and Guibet predicts NO concentrations

much lower that those measured in I.C engines. According to this mechanism, the

formation process is too slow for NO to reach equilibrium at peak temperatures and

pressures in the cylinders.



Detailed content of the Lecture:

Mechanism

of

NO

formation:

The nitric oxide formation during the combustion process is the result of

group of elementary reaction involving the nitrogen and oxygen molecules. Different

mechanism proposed is discussed below.

a.

Simple

reaction

between

N

2

and

O

2

N2 + O2  2 NO

This mechanism proposed by Eyzat and Guibet predicts NO concentrations

much lower that those measured in I.C engines. According to this mechanism, the

formation process is too slow for NO to reach equilibrium at peak temperatures and

pressures in the cylinders.

b.

Zeldovich

Chai

Reaction

mechanism:

L - 22